1. Field of the Invention
The present invention relates to an image pickup apparatus that includes a multistage retractable lens barrel.
2. Description of the Related Art
An image pickup apparatus, such as a digital still camera and a video camera, needs a high magnification of an image pickup lens and a miniaturization of a lens barrel configured to house the image pickup lens is required.
However, along with the high magnification of the image pickup lens, the number of optical units, such as a lens unit of the image pickup lens, and a moving amount of the optical unit are likely to increase and the sensitivity to the decentering or inclination of each optical unit becomes higher. As a result, it becomes difficult to miniaturize the lens barrel.
Japanese Patent No. 3898827 discloses a retractable lens barrel configured to guide the optical unit in the optical axis direction using a cantilever guide bar. In the lens barrel of Japanese Patent No. 3898827, one end is fixed onto the lens holder, and the other end guides the optical unit in the optical axis direction using a sliding guide bar that is supported by a holder of a fixture cylinder slidably in the optical axis direction. This lens barrel can increase the absolute position accuracy of each optical unit relative to the optical axis of the image pickup lens and the relative position accuracy between the optical units.
Japanese Patent Laid-Open No. 2002-350702 discloses a retractable lens barrel configured to support both ends of a guide bar inside of the first lens holder cylinder and to guide a second movement lens frame using the guide bar.
However, as a movement amount of each optical unit and an interval between the optical units increase along with the high magnification of the image pickup lens, a span of the guide bar increases and the lens barrel become large in a movement guide of the optical unit using the guide bar as disclosed in Japanese Patent No. 3898827 and Japanese Patent Laid-Open No. 2002-350702. When a long cantilever guide bar disclosed in Japanese Patent No. 3898827 is used, the optical unit guided by the guide bar is likely to decenter. In addition, in order to secure the rigidity of the cantilever guide bar, it is necessary to make large the support configured to cantilever the guide bar and to increase a diameter of the guide bar itself, causing a large size of the lens barrel. Moreover, when the sliding guide bar is used, the number of components used to hold the guide bar increases, the sliding guide bar and the optical unit guided by the sliding guide bar may incline due to scattering manufacturing errors of the components.